The Pew Research Center tracked the five most-viewed videos each week in the "news & politics" channel over a period of 15 months from January 2011 to March 2012.

The study reported that following the 2011 Japan earthquake, the 20 highest-watched news-related YouTube videos were about the event, accounting for more than 96 million views on the video-sharing site.

However, these videos weren't necessarily from big media outlets. Instead, most of the footage was compiled and produced by eyewitnesses from the tragedy, who then uploaded and posted it to the site. In turn, some of these videos were repackaged and posted by news organizations.

Though these first-person accounts can add a more personal touch to news reports, the viral sharing of such videos is creating problems.

The study claims in addition to citizens posting copyrighted material without permission, news organizations are also guilty of adding eyewitness-produced materials to its content without proper attribution to the original creator.

Citizens play a substantial role in supplying and producing footage. Morethan a third of the most watched videos (39%) were clearly identified as coming from citizens. Another 51% bore the logo of a news organization, though some of that footage, too, appeared to have been originally shot by users rather than journalists. (5% came from corporate and political groups, and the origin of another 5% was not identified.)

Citizens are also responsible for posting a good deal of the videos originally produced by news outlets. Fully 39% of the news pieces originally produced by a news organization were posted by users. (The rest of the most popular news videos of the last 15 months, 61%, were posted by the same news organizations that produced the reports.) As with other social media, this has multiple implications for news outlets. Audiences on YouTube are reshaping the news agenda, but they are also offering more exposure to the content of traditional news outlets.

The most popular news videos are a mix of edited and raw footage. Some pundits of the digital revolution predicted that the public, free to choose, would prefer to see video that was unmediated by the press. The most viewed news videos on YouTube, however, come in various forms. More than half of the most-viewed videos, 58%, involved footage that had been edited, but a sizable percentage, 42%, was raw footage. This mix of raw and edited video, moreover, held true across content coming from news organizations and that produced by citizens. Of videos produced by news organizations, 65% were edited, but so were 39% of what came from citizens.

Unlike in traditional TV news, the lengths of the most popular news videos on YouTube vary greatly. The median length of the most popular news videos was 2 minutes and 1 second, which is longer than the median length of a story package on local TV news (41 seconds) but shorter than the median length on national network evening newscasts (2 minutes and 23 seconds). But the variation in the length of the YouTube videos stands out even more. While traditional news tends to follow strict formulas for length, the most popular news videos on YouTube were fairly evenly distributed-from under a minute (29%), one to two minutes (21%), two to five minutes (33%) and longer than five (18%).

The study went on to say that in comparison, less than one percent of national network packages last longer than five minutes, while under five percent were less than a minute.